Telephone-transmitter.



W. W. DEAN. TELEPHONE TRAN$MITTER. I APPLICATION FILED P111323, 1906.

907,975. Patented Dec. 29, 1908.

. citizen er; the United States,

Elyria, in the county of Lorain and State of Ohio, have invented certain new and useful I enians snares rarest orrrcs.

WILLIAM W. DEAN, OF ELYRIA, OHIO, ASSIGNOR TO THE DEAN ELECTRIC COMPANY, OF

ELYRIA, OHIO, A CORPORATION OF OHIO.

TELEPHONE-TRANSMITTER.

so. some? pecification of Letters Patent.

Patented Dec. 29, 1908.

Application filed Februa y 23, 1906. Serial No. 302,544.

To all whom it mag concern:

Be it known that I, WILLIAM W. DEAN, a residing at Improvements in Telephone-Transmitters,

of which the following is a specification, reference being had therein to the accompany-- ing drawing. 1 My invention relates to telephone transmitters, and particularly to that type of instrurnent known in the art as solid back transmitters, in which granular carbon or finely-divided. material, such as powdered carbon, is used as the resistance-varying material.

It has for its object the production of an instrument of this class in whichthe parts shall be easy to assemble and adjust, without any sacrifice of accuracy or exactness, and which shall be highly sensitive and efficient when assembled and adjusted.

A further object of the invention is the production of an instrument in which the ,main diaphragm, constitutes the bottom'of the resistancechamber or button, andalso the front eleetrode.--

The highest type of granular transmitter known in the art today is that having a'sep arate resistance chamber or fbutt'on cone taining'the electrodes and the granular material supported" in proximity to the diaphragm, which is usually connected to one of the electrodes, while the other is rigidly fixed,

being attached to the frame of the instru-- ment by means of a bridge or its equivalent.

This type has been developed in man y forms, and is Widely used commercially, but in spite of this fact it is subject to certain draw-backs and defects inherent in the general design,

which prevent the attainment of full efficiency. One of the defects which I have discovered and have removed in the design presented herewith is the positive connection of both electrodes. In case of a very small variation in drilling or assembling, or in the punch that produces the central opening in the diaphragm, the parts will; not alineperfectly, and as the button is assembled. SQPfi-v rately with its two stemspresumablyper fectly alined', there isafinal slight distortion ofsthe auxiliary diaphragm' 'which creates. a

normal compressionstraingoiceaie side oi. the chamberand the disphragnniand atensicn on the other; The res'ultis-a drop in the individual instrument and a lack of uniformity in the ty o. Another defect is the fixed character 0 the ordinary containing cup which rmits the granules therein to pack or to E: fact that in the best solid-back transmitters a packed condition of the carbon may be roduced by placing the lips to the mouth-piece andexhausting the ail-from in front of the diaphragm. The latter buckles forward, the

car on drops into a mass, and when the diaphragm through its own resilience goes back to normal position the carbon is compressed into almost solidity. My invention is designed to obviate all of these difficulties, and otherswhich could be pointed out by way of example, but which are so apparent to those versed in the art as to need no explanation or criticism on my part.

The further objects of the invention will be elaborated in the specific description which follows, and more particularly pointed out in the appended claims. v 'My invention is illustrated in the accompanying sheet. of drawings, in which a single section of the transmitter is shown.

Referring now to the drawings A represents a circular front plate centrally apertured to receive the mouth-piece A, which is screwedinto said front plate. This mouth- 85 piece is preferably of hard rubber, and is provided with the perforated septum A adapted to protect the diaphragm of the instrument. The. plate A is-provlded upon its rear side with an annular face adapted to receive the diaphragm D, and in front of the diaphragm it is slightly recessed, as at a, to

form the sound chamber. Around the perip-hery of the plate I provide the rearwardlyextending posts a, and the annular bead a, upon which the inclosing casing'A is adapted to rest this being secured to the several posts a by screws, (not shown). Extending from side to side and resting upon two posts a is the bridge B, which is centrall apertured at B to receive the neck I) of t e boss B, which is insulated from but secured to the bridge by screws b'b which pass through hushed openings in the bossB. The inclosing shell A. has its central rear-portion flattened and provided with suitable :apen.

tures ILL-c, the former of whichis adapted to admit the line conductors to the circuit terminals (r -a of. the. instrument, and the latter of which is. adapted to receive the se- 1.10

packed. It is a well known secured the supplemental diaphragm D, of

mice, by means of the clamp nut e which in this instance also serves as the binding nut for one of the circuit terminals.

Secured to the supplemental diaphragm D by an annular retaining ring C is the resistanee cup which in this instance comprises a flanged ring 0, the main diaphragm D constituting the bottom of what is known as the resistance button. The diaphragm is gold-plated or platinum-faced upon its inner side, and constitutes the front electrode of the instrument.

Mounted upon the bridge by means of a boss 8, which is centrally apertured and bushed with insulating material to prevent contact with the bridge, are pressure springs S, (only one of which is shown), which are adapted to bear upon the annular retaining ring C and force the resistance cup C into engagement with the diaphragm. A bolt S is adapted to' pass through the bushed opening of the boss S so as to hold the springs in place, and at the same time afford a binding post for the other circuit terminal of the instrument.

The circuit of the instrument is as follows: from bolt S, spring S, retaining ring 0 re sistance cup 0, diaphragm D, resistancevarying material C, rear electrode E, shank e, and out to line..

In assembling the instrument the diaphragm is-insulated from the front plate A by the soft rubber band (1, which is stretched around its peri hery, and is held in place by the pressure 0 the resistance cup C as exerted thereon by the springs S. The separate damper springs commonly used with this type of instrument I find I do not need, the springs S erforming their function perfectly. In fact,tiie damping action of the springs S being symmetrical, and communicated to the diaphragm through the resistance chamber over a suitable central area, is much superior to that of the ordinary springs, and from this,

emanatesa part of the su eriority of my instrument. After the diap ragm has been seated against the face a of thefront plate A, the bridge B, with the resistance chamber connected thereto and substantially filled with resistance-varying material, is secured in position upon the flange a by the screws a. The set-screw which holds the stud e in place Within the apertured boss B is new the inherent resiliency ad ust thestud e to its proper position withunscrewed so as to allow the springs S, and of the diaphragm to in the boss. After this the set-screw is tightened and the rear electrode fixed so that subsequent vibrations of the main diaphragm D are taken up by the springs S and the supplemental diaphragm d.

The operation of this transmitter is suf- 'liciently apparent from the above description, when taken in connection with the accompanying sheet of drawings, to obviate any further description. It is however evident that the resistance chamber and its accompanying parts are not carried by the diaphragm, nor is it positively connected thereto, yet the sprin s S maintain a soil]- ciently intimate contact and a heavy enough pressure to insure most excellent transmission of the vibratory motion of the diaphragm to the cup, and, as the diaphragm D is plated or platinum-faced on its entire inner side, it is immaterial if the cup is not accurately centered with reference thereto. The parts, however, are self-centering, and the granular carbon or other resistanccvarying material in the cup is constantly agitated to prevent its packing. The instrument is economical to maimtacture, simple to assemble, and eflicient in use. The cup may be provided with sharp edges to engage the diaphragm so as to make a tight joint, if desired, but this is not essential.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a telpphone transmitter, a vibrating I diaphragm constituting an electrode, an in dependently supported resistance cup, said diaphragm constituting the bottom of said cup, a second electrode in said cup, an auxiliary diaphragm peripherally secured to the cup, and centrally secured to the fixed electrode, and means for holding the cup in en gagement with the diaphragm so that it is vibrated thereby.

2. In a telephone transmitter, a vibrating diaphragm constituting one electrode, a re sistance cup independently supported with respect to the diaphragm, a second electrode in said cup, an auxiliary diaphragm peripherally secured to the edge of the cup and connecting the same with the fixed electrode, granular carbon between the electrodes, and springs engaging the resistance. cup and adapted to hold the same against the diaphragm so that it is vibrated thereby.

3. In a telephone transmitter, the co mhination with a resilient diaphragm, of a fixed electrode, a cup formed of inflexible material surrounding said electrode and having its edges resting against the diaphragm, a ilexible connection between the cup and the fixed electrode, granular material in the cup, and spring pressure means adapted to force Y so is to put the same'under initial tension.

surrounding. the fixed electrode and with its 5 edges independentof but resting against the i resilient diaphragm,granular material in the 5 the cup into engagement With the diaphragm cup, and spring pressure means adapted to 10 force the cup against the diaphragm to put '4. In a telephone transmitter, the co1nbi-" the same under initial tension; nation with a resilient diaphragn coated on In testimony whereof I affixmy signature its inner face to form an electrode, affixed in presence of two witnesses. electrode, :1 011}? formed of inflexible material i WILLIAM W. D EAN Witnesses:

RAY -H. MANSON, S. A. BEYLANI). 

